Device for forming and heat bonding gusset corners of a folding box blank bearing a thermoplastic coating



May 12, 1970 s. J. HOYRUP 3,511,140

DEVICE FOR FORMING AND HEAT BONDING GUSSET CORNERS OF A=FOLDING BOXBLANK BEARING- A THERMOPLASTIC COATING Filed July 1, 1968 4 Sheets-Sheet1 INVENTOR. Jz'gura J Haj/up May 12, 1970 s. .1. H RU 3,511,140

DEVICE FOR FORMING AND '1 BO ING .GUSSET CORNERS ARING OF A FOLDING BOXBLANK BE A THERMOPLASTIC COATING Filed July 1, 1968 4 Sheets-Sheet 2INVENTOR. Sigurd J. Hay/up I A TTOR/VEY May 12, 1970 s J. HOYRUP3,511,140

HEAT BONDING DEVICE F FORMING GUSSET CORNERS A FOLD OX BLANK BEARlNG ATHER AS'IIC COATING Filed July 1, 1968 4 Sheets-Sheet 5 INVENTOR.Jzgurc/ J. Hay/0,0

(ML, A TTOR/VEY May 12, 1970 5. J. HOYRUP 3,511,140

DEVICE FOR FORMING AND HEAT BONDING GUSSET CORNERS OF 'AAFOLDING BOXBLANK BEARING A THERMOPLASTIC COATING 4 Sheets-Sheet 4 Filed July 1,1968 INVENTOR. Sigurd J Hay/11,0

a4, ATTORNEY United States Patent DEVICE FOR FORMING AND HEAT BONDING-aware Filed July 1, 1968, Ser. No. 741,616 Int. Cl. B31b J/44 U.S. Cl.351 6 Claims ABSTRACT OF THE DISCLOSURE The gusset corner portions of abox blank bearing a preapplied thermoplastic coating are heated, whilethe blank is still in its fiat state, by jets of compressed heated airapplied from opposite surfaces. A higher coating temperature is producedon one surface than on the opposite surface, thereby reducing thestiffness of the corner portion preparatory to the folding of the gussetcorners. The higher coating temperature is achieved by nozzles directedagainst the undersurface from which the blank is closely spaced byelements which also assist in the folding of the gusset diagonals. Therelatively cooler side of the blank comes to lie against the surface ofa plunger which forces the blank through a folding die to fold and bondthe corner gusset panels in a known manner.

It is known to erect and adhesively bond the corners of agusset-cornered folding box from an appropriately designed fiat boxblank bearing a preapplied coating of thermoplastic material on oppositesurfaces. According to known practice the blank is partially prefoldedby a transport device which carries the blank to a forming die at thecorners of which heating elements are installed. The cold blank isprefolded to the extent that its corner gussets make surface-to-surfacecontact with the heating elements or blocks which act on the blankduring a period of dwell from the moment the blank is deposited by atransport device until the moment a forming plunger engages the blank tocomplete the folding operations and effect the bonding of the cornerareas while the blank passes through the die.

In high-speed production difficulties arise which have their cause inthe relatively high degree of stiffness of paperboard which is plasticcoated on opposite surfaces. If the board is bent abruptly, particularlyin the process of prefolding of the corner gussets preparatory to movingthe gusset panels into contact with the rectangular heating blocks, theboard frequently tears at, or near, the gusset diagonal. Also thecreasing of the relatively stiff board at its fold lines is often notprecise, resulting occasionally in a misshapen corner. In order toreduce such inaccuracies, the transport devices have been fitted withrules or blades acting on the blank at the folding scores to insure thatthe paperboard creases along the crease scores previously impressed inthe blank by the cutting and creasing die. Such supplementary prefoldingmeans on the transport device complicate the machinery and requireexchange or adjustment every time the box size is changed.

Other problems arise by the transfer of soft thermoplastic adhesive ontothe heating blocks during heating of the coating and/or onto the plungerduring the box erection procedure.

The present invention is based on several related considerations whichwill be stated irrespective of their order of importance.

It is realized that paperboard used for the packaging of frozen foodsforwhich gusset-cornered boxes are primarily employed-is a board ofconsiderable initial stiffness. The stiffness is increased by thethermoplastic coating on opposite surfaces. It is realized that theboard stiffness can be reduced considerably, particularly at the gussetcorner areas by the softening of the coating while the blank is still inits flat condition, thereby facilitating the subsequent foldingoperation.

It is further realized that the heating of the board may be carried to ahigher degree on the surface of the blank which becomes the outside ofthe box without danger of transfer of adhesive, and that the heating ofthe surface which becomes the inside of the box should be carried to alesser degree in order to reduce the danger of transfer of adhesive ontothe plunger.

It is also realized that differential heating produces stress in theboard in a sense to cause a desirable tendency of the blank to curl inthe direction in which the blank is to be folded.

It is further realized that differential heating can be produced by twojets or streams of compressed heated air of initially the sametemperature, one being of greater length than the other and, for thisreason, subject to expansion cooling to a greater degree than the other,thereby eliminating the need for separate sources of heated air ofdifferent temperature. This principle is disclosed in my copendingapplication Ser. No. 571,264 filed Aug. 9, 1966, now Pat. No. 3,394,635,dated July 30, 1968.

In addition, it is realized that in order to keep the board temperaturewithin close limits the spacing of the blank surface from the nozzlesemployed for high temperature heating must be very accurately gauged andthat the element used for the purpose of spacing may be made to performthe additional function of creasing the corner gussets at theirdiagonals.

These and other considerations, objects and advantages of this inventionwill appear more fully from the detailed description which follows,accompanied by drawings showing, for the purpose of illustration, apreferred embodiment of the invention. The invention also resides incertain new and original features of construction and combination ofelements, as well as steps and sequences of steps hereinafter set forthand claimed.

Although the characteristic features of this invention which arebelieved to be novel will be particularly pointed out in the claimsappended hereto, the invention itself its objects and advantages and themanner in which it may be carried out may be better understood byreferring to the following description to be taken in connection withthe accompanying drawings forming a part of this disclosure in which:

FIG. 1 is a perspective view of a plunger, die and blank transportmechanism comprising preheating and gusset folding assemblies at the diecorners;

FIGS. 2 and 3 are perspective views of two sequential operationsperformed on a blank by the mechanism of FIG. 1; and

FIG. 4 is a perspective view of the underside of the mechanism of FIGS.1 to 3 illustrating the completion of the box folding operation.

In the following description and in the claims various details will beidentified by specific names for convenience. The names, however, areintended to be generic in their application. Corresponding referencecharacters refer to corresponding parts in the several figures of thedrawings. The drawings accompanying, and forming part of, thisspecification disclose certain specific details of construction for thepurpose of explanation of broad aspects of the invention, but it shouldbe understood that structural details may be modified in variousrespects Without departure from the principles of the invention and thatthe invention may be incorporated in, and practiced by, other structuresthan shown.

Referring to FIG. 1, the lower portion of a box forming plunger 11 andthe vacuum cups 12 of a blank transport device 13 of conventionalconstruction are seen above a forming die whose interior or shaft isdesignated 14.

The die comprises side folding elements 15, 16 and end folding elements17, 18 for folding into box shape a flat blank placed over the die anddriven into the die 14 by the plunger 11.

Four heating devices are mounted above, and somewhat outside the shaftof, the die. Of these heating devices the pairs located at oppositediagonal corners of the die are identical.

The heating devices are essentially hollow bodies comprising a pluralityof air discharge apertures or nozzles supplied with heated compressedair through appropriate ducts from a source of compressed air via heatexchangers 21, 22 (FIG. 4). Heat exchanger 21 serves heating devices 19,at the left of FIG. 1 and heat exchanger 22 serves heating devices 19,20 at the right.

A riser duct 23 extends upwardly from each heat exchanger, the riserhaving a T at the top which discharges into L-fittings 24 telescopicallyfitting over the arms of the T. The L-fittings 24, in turn,telescopically fit over nipples 25 which are integral with the hollowbodies 19 and 20, respectively.

Each hollow heater body comprises a horizontally extending L-shapedportion 26 comprising a plurality of air discharge apertures 27 arrangedin an L pattern, and a vertically extending portion 28 which has aplurality of steps or corrugations formed on the surface facing the die,there being three steps in the illustrated form. Such steps are suitablyformed by machining V-grooves 29 which extend horizontally across theface of the body. The air discharge apertures 30 are provided in thedownwardly facing portions of the steps, there 'being three tiers ofapertures in each of the heater bodies.

Air is discharged through these apertures or nozzles 30 in downwardlyslanted direction against the surface of a blank (see FIG. 2) overlyingthe L-shaped horizontal heater portions. By reason of the inclination ofthe surfaces in which the nozzle apertures 30 are formed the latter arebarely visible in the figures.

Physical contact between the blank to be heated and the horizontalheater body portions 20 is prevented by spacer elements. These aresuitably in the form of vertically disposed blades 31 rounded off towardthe die apertures as seen at 32. The blades 31 approximately vbisect anL-angle and for this reason extend at an angle of approximately degreesto the vertical portions of the folding elements 15 to 18. The topportions of the blades 31 project above the top surface of the Lportions 26 and thus maintain the blank at an accurately gauged distancetherefrom.

The operation of the heating mechanism is best explained by reference toFIG. 2 showing a flat blank A deposited on the spacer blades by theblank transport device 12, 13.

In the deposited position the outer edges of the blank are caughtbetween aligning posts 33, some of which are serrated or threaded at 34in order to prevent a deposited blank from escaping after withdrawal ofthe transport device.

The blank A comprises a bottom panel 35, a cov er panel 36 and a rearwall panel 37 therebetween. The box body portion of the blank comprisesfurther a front panel 38 and end panels 39, 40.

The bottom fold lines along which the wall panels 37, 38, 39 and 49 arearticulated to the bottom panel 35 are numbered 41, 42, 43, 44. Theirextensions define corner gussets of which each corner comprises a pairof gusset panels 45, 46 articulated to each other along a diagonalcrease 47.

The cover portion of the blank comprises a cover front flap 48 and coverend flaps 49, 50 articulated to the cover panel 36 along folding scores51, 52 ,and 53, respectively.

In deposited position the spacer blades 31 underlie the gusset diagonals47 and keep the blank out of physical contact with the heating devices19, 20.

Heated air issuing from the upwardly directed nozzles heat the undersideof the blank to a relatively high temperature due to the fact that thetemperature loss of the air attributable to expansion of the compressedheated air in the surrounding atmosphere is relatively small. The airblast heats the entire corner areas of the blank and the stiffness ofthe thermoplastic-coated blank is correspondingly reduced at the scoreswhich define the gussets.

As the surface temperature produced at the underside of the blankexceeds the temperature of the top surface of the blank, the blank has atendency to curl upwardly, in which sense the wall panels and gussetpanels are about to be folded.

While the blank corners at the underside are being heated to a hightemperature, the top surface is heated to a lesser temperature by theair blast issuing from the downwardly directed nozzles 30 from which theheated air travels a considerably longer distance to the blank surface,at least twice as far as the air from the underside. The air impacttemperature at the blank is correspondingly lower and is so selectedthat the plastic coating remains sufficiently non-tacky, so that it willnot adhere, nor transfer adhesive, to the walls of the plunger 11 in thesubsequent folding operation (FIG. 3).

It will be noted that the blank transport device 12, 13 is free from anyblank-precreasing devices for prebreaking the bottom scores and thegusset scores as were previously required and employed in order toovercome the stiffness of thermoplastic coated blanks.

Immediately after the instance illustrated in FIG. 2 the vacuum cups 12of the blank transport device release the blank, whereupon the transportdevice 13 is retracted and the plunger descends (FIG. 3).

The blank creases at the bottom fold lines, the corner gusset panels arecreased at their diagonals 47 by the assistance of the spacer blades,and the corner gussets are folded into shallow recesses 56 provided inthe plunger ends to accommodate the additional two thicknesses of boardat that area.

The zones of highest surface temperature of the blank are on theunderside of the blank and are substantially limited to the gussetpanels which are pressed together when the plunger enters the die.

High bonding pressure is executed on the folded corner gussets byrollers 57 past which the plunger 11 moves the blank. The rollers aremounted on axles 58 fixedly supported in depending arms 59 which arepivotally supported on the understructure of the die at 60 and are urgedtoward the plunger by compressed helical springs 61.

In the position shown in FIG. 4 the blank has assumed box shape A, itscorners are bonded after having passed the rollers 57, and the box isabout to be discharged.

The plunger 11 has only a short additional distance to travel in orderto reach the bottom end of the stroke which brings the top edge of thebox body beyond catches or strip-off fingers 62. These prevent the boxfrom following the plunger on its upward return stroke.

Air is supplied to the heat exchangers (not shown) from a suitablecompressor through relatively large flexible ducts of which one isvisible at 63. The plunger may be fitted with cooling ducts 64 throughwhich a cooling liquid may be circulated (FIG. 3).

EXAMPLE The device was operated at the rate of boxes per minute.

Total air volume: 3 cu. ft./min. (8S l./min.).

Air temperature measured within discharge nozzles 27 and 30: 930 F. (500C.).

Air impact temperature on underside of gusset panels: 600 F. (315 0).

Air impact temperature on top surface of gusset panels: 420 F. (215 C.).

Extent of heated area: Beyond bordering scores of gussets.

Corner bond failure as determined by tearing apart and examining thegusset areas for tearing of fibres: No failure in 50 successive boxes.

What is claimed is:

1. In a device for forming and heat bonding gusset corners of a foldingbox blank bearing a coating of thermoplastic adhesive, the devicecomprising a plunger and a die through which the plunger forces theblank, and means at the die corner for applying heat to the blank, theimprovement which is characterized by the heating means comprising anupwardly directed first nozzle means for discharging heated air againstthe underside of a flat blank placed thereover and a downwardly directedsecond nozzle means for discharging heated air against the top side ofthe blank, the first nozzle means being disposed below the blank, thesecond nozzle means being disposed adjacent to and above the blank, anda spacing means for supporting the blank at a distance above, and out ofcontact with, the first nozzle means, the second nozzle means being sodisposed as to cause the air discharged therefrom to travel at leasttwice as far to the blank as the air discharged from the first nozzlemeans when the blank is in contact with said spacer means, both saidnozzle means being supplied from the same source of heated compressedair.

2. The device according to claim 1 in which the first nozzle meanscomprising nozzle apertures disposed in an angular outline and in whichthe spacing means is positioned between the legs of the angle.

3. The device according to claim 1 in which the second nozzle meanscomprises downwardly directed discharge apertures arranged in twosubstantially horizontal tiers which are vertically spaced from eachother and from the first nozzle means.

4. The device according to claim 1 in which the first and the secondnozzle means are combined into a single housing supplied with heatedcompressed air through a single duct.

5. In the method of erecting a flat gusset cornered box blank intohollow box shape and bonding the gusset panels together and to a boxwall -by means of a preapplied coating of a thermoplastic adhesive andinvolving the heating of the coating to a state of tackiness and theforcing of the blank through a folding die by means of a plunger toerect the blank, fold the corner gusset structure, and bond the gussetpanels together and to a box wall, the step of applying, while the blankis still flat, compressed heated air to opposite surfaces of the cornergussets, thereby reducing the resistance to folding of the gussets alongthe folding scores which define the gusset.

6. The method according to claim 5 in which that surface of the blankwhich becomes the outside of the box is acted on by air of higher impacttemperature than the surface which becomes the inside of the box.

References Cited UNITED STATES PATENTS 3,028,798 4/1962 Allen. 3,085,4794/1963 Hoyrup et al. 9351 3,192,837 7/1965 Hoyrup et al. 93-51 BERNARDSTICKNEY, Primary Examiner

